Food patties of various kinds, including hamburgers, molded "steaks", fish cakes, poultry patties, pork patties, and various vegetable patties are frequently molded in high volume automated molding machines Patty molding machines successfully adaptable to the forming of any of these food products are described in Richards Reissue U.S. Pat. No. Re. 30,096, reissued Sep. 18, 1979; Sandberg et al U.S. Pat. No. 4,054,967, issued Oct. 25, 1977; LaMartino et al U.S. Pat. No. 4,128,003, issued Jan. 8, 1980; Sandberg et al U.S. Pat. No. 4,356,595, issued Nov. 2, 1982; Sandberg U.S. Pat. No. 4,697,308, issued Oct. 6, 1987 and Lindee U.S. Pat. No. 4,872,241, issued Oct. 10, 1989.
Although any of these machines, and others as well, are capable of producing food patties of consistent size, weight and configuration on a high volume basis, substantial problems may be encountered when the machines are required to mold patties from food products which, unlike hamburger, have not been ground to relatively small particle size. Thus, it may be desirable to form patties from a food product that has not been chopped or ground; the starting material may consist of whole poultry breasts, large segments of pork or other meat, large fish fillets, or relatively large pieces of almost any food product that has an appreciable fiber content. Even in those machines specifically adapted to processing whole-fiber food products (e.g., Sandberg U.S. Pat. No. 4,697,308) maintenance of good texture in the finished patties may be a continuing problem.
The molding mechanism of the Richards reissue U.S. Pat. No. Re. 30,096, also used in the specific machine illustrated in Sandberg U.S. Pat. No. 4,697,308, utilizes a horizontally oriented manifold valve cylinder having two longitudinally displaced inlet slots which are alignable with respective outlet slots of two of side-by-side food pump cavities. The manifold valve cylinder has an elongated outlet slot which is angularly skewed longitudinally of the manifold valve cylinder to control the outlet pressure from the manifold to a molding mechanism. In later modifications of this molding mechanism, which are shown in U.S. Pat. Nos. 4,356,595; 4,697,308 and 4,872,241, the elongated outlet slot from the manifold valve cylinder to the mold cavities is angularly enlarged to better handle fibrous food products containing large pieces with minimum deterioration of the large pieces and with no more than minimum distortion of the food patties when later cooked. The flow path of the food product through the modified manifold valve cylinder, whether ordinary hamburger or a high-fiber product, still requires a reversal of the direction of flow of the food product as one pump cavity outlet is closed by rotation of the manifold valve cylinder and the other outlet is opened, because each outlet discharges directly into only one end of the manifold valve cylinder, the end adjacent to its cavity.
The rotation of the manifold valve cylinder to open and cylinder to open and close the pump cavity outlets tends to reduce the muscular texture of large pieces of a fibrous food product, due to shearing of these large pieces. The relatively small inlet and outlet openings in the manifold valve cylinder may create a large pressure drop as food products are pumped through this valve. Another problem which occurs because of the use of the relatively small inlet and outlet openings in the manifold valve cylinder is the tendency of large segments, in fibrous food products, to clog the manifold valve cylinder because of the inability to easily pass through these openings. Other operating problems with this basic mechanism may include undue "working" of the food product due to repeated reversals in flow direction, a need for higher pump pressures than desirable, and a tendency for some part of the food product to remain stationary or "freeze" in the manifold valve cylinder.